/*
 * Copyright 2012-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cn.springcloud.gray.bean.properties.bind;

import cn.springcloud.gray.bean.properties.source.ConfigurationPropertyName;

/**
 * Callback interface that can be used to handle additional logic during element
 * {@link Binder binding}.
 *
 * @author Phillip Webb
 * @author Madhura Bhave
 * @since 2.0.0
 */
public interface BindHandler {

    /**
     * Default no-op bind handler.
     */
    BindHandler DEFAULT = new BindHandler() {

    };

    /**
     * Called when binding of an element starts but before any result has been determined.
     *
     * @param <T>     the bindable source type
     * @param name    the name of the element being bound
     * @param target  the item being bound
     * @param context the bind context
     * @return the actual item that should be used for binding (may be {@code null})
     */
    default <T> Bindable<T> onStart(ConfigurationPropertyName name, Bindable<T> target,
                                    BindContext context) {
        return target;
    }

    /**
     * Called when binding of an element ends with a successful result. Implementations
     * may change the ultimately returned result or perform addition validation.
     *
     * @param name    the name of the element being bound
     * @param target  the item being bound
     * @param context the bind context
     * @param result  the bound result (never {@code null})
     * @return the actual result that should be used (may be {@code null})
     */
    default Object onSuccess(ConfigurationPropertyName name, Bindable<?> target,
                             BindContext context, Object result) {
        return result;
    }

    /**
     * Called when binding fails for any reason (including failures from
     * {@link #onSuccess} calls). Implementations may choose to swallow exceptions and
     * return an alternative result.
     *
     * @param name    the name of the element being bound
     * @param target  the item being bound
     * @param context the bind context
     * @param error   the cause of the error (if the exception stands it may be re-thrown)
     * @return the actual result that should be used (may be {@code null}).
     * @throws Exception if the binding isn't valid
     */
    default Object onFailure(ConfigurationPropertyName name, Bindable<?> target,
                             BindContext context, Exception error) throws Exception {
        throw error;
    }

    /**
     * Called when binding finishes, regardless of whether the property was bound or not.
     *
     * @param name    the name of the element being bound
     * @param target  the item being bound
     * @param context the bind context
     * @param result  the bound result (may be {@code null})
     * @throws Exception if the binding isn't valid
     */
    default void onFinish(ConfigurationPropertyName name, Bindable<?> target,
                          BindContext context, Object result) throws Exception {
    }

}
